As a result of recent accelerated industrial development, serious damage due to noise has been increased. Thus, various acoustic absorption materials had been developed, and wasted tire chips, cork and foam rubber was mainly used as the conventional acoustic absorption materials. These acoustic absorption materials are low-priced and eco-friendly, but have some disadvantages that they have a non-uniform filled thickness and a slow working speed and also a crack may be generated. Further, in case of the cork or the foam rubber, they have a uniform filled thickness and an excellent constructability, but also have some disadvantages that they have a complicated working process and a separated gap and also the crack may be generated.
Therefore, there have been developed various acoustic absorption materials like an acoustic absorption board made of polyester fiber, or made by foaming resin such as urethane, polypropylene, polyethylene and the like.
However, in case of the acoustic absorption material made of polyester fiber, if liquid flame retardant is added to manufacture an acoustic absorption material having flame retardancy, there are some problems that, since a weight of the acoustic absorption material is considerably increased, it is inconvenient to convey it and also it is difficult to carry out a construction work.